Too bad she didn't do it a cappella, or I'd remix it. Her voice is pretty good, but the mix is messy. The instruments and background vocals clash with the vocals so that it's hard to make anything out.

I don't have good tools for video editing, and running it through Windows Live Movie Maker made both the video and audio worse, so I'm just attaching the audio since it's in a fairly high quality format. Feel free to splice it to video if you'd like.

Mostly I toned down the vocals about a bit, so they are not quite so grating and harsh sounding when she's too loud, pulled up the mid-lows and highs to bring out the guitar a bit more, threw in some asymmetric delay and a little reverb for some depth. I might have overdone the reverb (I'm not a big fan a reverb), but that is partly a matter of taste. A lot of people tend to like it.